A portion of the engine oil present in the crankcase of an internal combustion engine is in the form of droplets suspended in the air. During the operation of the engine, some of the gases present in the combustion chamber pass through a gap between the pistons or piston rings and the cylinder walls and enter the crankcase. These gases are known as blow-by gases. In the crankcase, the blow-by gases mix with the oil droplets. This mixture of blow-by gases and oil cannot be safely exhausted directly to the atmosphere. One solution consists in returning the mixture to the engine's induction system to be re-combusted. However, combusting a mixture containing oil is undesirable as it creates a substantial amount of pollutants. Therefore, in order to reduce pollutants produced by the engine, the oil droplets must first be removed from the mixture such that only the blow-by gases are re-combusted.
The prior art describes various ways in which this can be achieved, such as by using a cyclone separator. U.S. Pat. No. 5,261,380 discloses a ventilation system for an automotive engine having a crankcase, an induction system, a crankshaft, and at least one camshaft. A processor pumps gases from the crankcase and separates entrained lubricating oil from the pumped gas flow. A recovery apparatus introduces the separated gas to the induction system while returning the separated oil to the crankcase. However, the disclosed solution has a complicated structure and requires a lot of space. Therefore, there is a need for an engine blow-by gas ventilation system which has a relatively simple construction and is relatively simple to manufacture while being reliable.